crash plan —

How best to clean out satellites before they become space garbage?

Looking at options for quick and safe de-orbiting.

Space is getting crowded with old satellites and communication detritus, but scientists are still lacking an effective method of clearing out the clutter, according to a paper published in the March/April edition of the Journal of Spacecraft and Rockets. Satellites that simply go defunct are generally left to decay and fall to Earth in potentially lethal pieces—or worse, collide with functioning satellites. These are unnecessary risks when we could be using devices like the inflatable drag-inducing balloons and electromagnetic tethers at our disposal.

In the paper, researchers describe and examine a number of methods for drawing decommissioned satellites out of orbit and away from their functional brethren. The risks of not doing so are obvious; the authors cite the case of the out-of-service Russian satellite Cosmos 2251, which collided with the functional Iridium 33 satellite in Feburary 2009. Both satellites were destroyed and fell in over 2,000 potentially lethal pieces to Earth. To determine the best method for getting space detritus out of low-Earth orbit, the researchers encourage the consideration of metric called “area-time product” (the cross-sectional area of the de-orbit apparatus multiplied by the time it would take to de-orbit the satellite) to evaluate which approach is best.

One proposed method of drawing down satellites that are just taking up space is electromagnetic tethers, which use a power supply to create a flow of electrons within a conductive tether that interacts with Earth’s magnetic field to draw the satellite slowly down to Earth. But electromagnetic tethers work slowly and have a large cross-section, so in a sense they increase the risk of interrupting other satellites while trying to get the defunct one out of the way.

Another option is an inflatable attachment that increases the drag on the satellite and slows its orbit. The authors of the paper propose ultrathin envelope spheres, which don’t require a power supply of the size that an EM tether does, but it would take only a matter of months to draw the satellite down to Earth. Because it works so quickly, the envelope would greatly reduce the risk of collisions despite the temporary added girth.

Casey Johnston
Casey Johnston is the former Culture Editor at Ars Technica, and now does the occasional freelance story. She graduated from Columbia University with a degree in Applied Physics. Twitter@caseyjohnston

Can someone provide some info on how much drag a satellite has on it anyway, and then how much extra these balloons would add? I'm thinking these balloons would have to be huuuge, but then I don't know the science well enough.

It really sucks that we don't seem to have any recycling capability for satellites. We spend millions to get these things in the sky, and every pound counts. You'd think a permanently spaceborne shuttle that goes around retooling and re-orbiting the damn things would be cost effective by now... Then again, given how much we like to ignore the space programs as time goes on...

Big flaw in this article. Pieces of satellites falling back to Earth are not a problem. They mostly burn up, and even if not, the odds of hitting anyone are negligible. You should be more worried about snakes on planes, or dying of a heart attack due to sudden surprise at winning the lottery, than "potentially lethal" falling debris.

However, pieces of satellites that STAY in orbits used by other things can become a huge problem, called Kessler Syndrome

It really sucks that we don't seem to have any recycling capability for satellites. We spend millions to get these things in the sky, and every pound counts. You'd think a permanently spaceborne shuttle that goes around retooling and re-orbiting the damn things would be cost effective by now... Then again, given how much we like to ignore the space programs as time goes on...

Just chump change to toss a satellite up there compared with manned missions.

It really sucks that we don't seem to have any recycling capability for satellites. We spend millions to get these things in the sky, and every pound counts. You'd think a permanently spaceborne shuttle that goes around retooling and re-orbiting the damn things would be cost effective by now... Then again, given how much we like to ignore the space programs as time goes on...

Seriously, this does sound like the a makings of a business venture. Considering the materials used. But also shouldn't the companies that launch these satellites to arrange for their disposal.

On a not so serious note: I'm trying to imagine the faces at the local recycler when I pull up with a satellite on the trailer.

Big flaw in this article. Pieces of satellites falling back to Earth are not a problem. They mostly burn up, and even if not, the odds of hitting anyone are negligible. You should be more worried about snakes on planes, or dying of a heart attack due to sudden surprise at winning the lottery, than "potentially lethal" falling debris.

However, pieces of satellites that STAY in orbits used by other things can become a huge problem, called Kessler Syndrome

I'm sorry... while most pieces will burn up, there are some pretty large chunks falling to earth. When UARS crashed down in 2011 they predicted 26 pieces would not burn up, and estimated a 1 in 3,200 chance of a person being hit. While improbable, hardly a non-issue, and not a "Big flaw" in the article.

It really sucks that we don't seem to have any recycling capability for satellites. We spend millions to get these things in the sky, and every pound counts. You'd think a permanently spaceborne shuttle that goes around retooling and re-orbiting the damn things would be cost effective by now... Then again, given how much we like to ignore the space programs as time goes on...

Why not just ensure there's enough fuel in the adjustment thrusters to put it on a collision course with the sun? That way we don't have to worry about the space junk on Earth, and we get rid of a defunct satellite. Kills two birds with one stone.

That's actually a great idea. The logic to make the correction to break earth orbit and aim to the sun could be pre-programmed and remotely triggered. Then, do this with all satellites that need to be decommissioned and add some lightweight networking equipment on them to create a daisy-chained network of decommissioned satellites heading to the sun to relay back to earth any available scientific data via the satellite daisy chain.

Why not just ensure there's enough fuel in the adjustment thrusters to put it on a collision course with the sun? That way we don't have to worry about the space junk on Earth, and we get rid of a defunct satellite. Kills two birds with one stone.

Do you know how much fuel is needed, and how big an engine, to get from 7.4 km/s to 11.2 km/s (minimum)???

Why not just ensure there's enough fuel in the adjustment thrusters to put it on a collision course with the sun? That way we don't have to worry about the space junk on Earth, and we get rid of a defunct satellite. Kills two birds with one stone.

One word: mass. Specifically, mass is very expensive to launch into orbit. Building and fueling a satellite with enough prop to not only do its mission but then escape Earth orbit is prohibitively expensive, especially considering the myriad opportunities that are comparatively cheap, like burning back into the atmosphere.

Why not just ensure there's enough fuel in the adjustment thrusters to put it on a collision course with the sun? That way we don't have to worry about the space junk on Earth, and we get rid of a defunct satellite. Kills two birds with one stone.

Assuming this isn't sarcasm (which is possible given the fun turn the comments have taken), The amount of thrust and fuel to climb out of Earth's gravity well is much larger than you think.

If we take all the unused satellites out of orbit, how are we ever going to have enough out there at the end of the environmental apocalypse to impact Wall-E on his way into space? Think of the CHILDREN!

I don't know why a small explosive charge (or even gas) is used to propell a drag chute line down into the upper atmosphere where it will expand and slow the craft down. The with a controlled release of the drag cute, they could be controlled to splash down in the pacific.

The main problem with the argument is that any solution to remove defunct satelites could be used as an anti-satellite weapon.

And since almost every nation on the planet agreed to not weaponize satellites, I don't see how any solution could pass international support.

How would tethers be used as an anti-satellite weapon? Drag-increasing airbags?

If you deorbit enemy satellites, you've stripped them of essential wartime information. You could then proceed to make a blitzkrieg, and they would have no way of knowing what is coming for them... it's an act of aggression.

I don't know why a small explosive charge (or even gas) is used to propell a drag chute line down into the upper atmosphere where it will expand and slow the craft down. The with a controlled release of the drag cute, they could be controlled to splash down in the pacific.

Ick. A space tether. That was attempted once and it was... a disaster?

You'd be deploying a frozen parachute which sat folded up in a small box in space for many years, on the end of a tether at least a few tens of miles long to make it worth it, using explosives?

A mandate to include deorbit thrusters on all satellites makes sense, and it is in fact one of only two viable options. (The other one being a space-shuttle like craft which could rendezvous with satellites and pull them into its cargo bay.) But even with a deorbit thruster, controlling the precise re-entry point is hard! Really really hard. The satellite will be tumbling and pieces will be melting and falling off, all of it changing its aerodynamic properties. Without the atmosphere this would be dead-easy of course. It's so hard that it may not be possible to predict which orbit the satellite would go down on, let alone where on Earth (which is inconveniently rotating below). Deorbit thruster would be a costly and risky and a probable solution.

One other problem exists. A derelict satellite falling on something is an accident. Deorbiting a satellite and having it fall in the wrong place is negligence.

The main problem with the argument is that any solution to remove defunct satelites could be used as an anti-satellite weapon.

And since almost every nation on the planet agreed to not weaponize satellites, I don't see how any solution could pass international support.

How would tethers be used as an anti-satellite weapon? Drag-increasing airbags?

If you deorbit enemy satellites, you've stripped them of essential wartime information. You could then proceed to make a blitzkrieg, and they would have no way of knowing what is coming for them... it's an act of aggression.

I understand why anti-satellite weapons are bad.

My question was how those solutions pose an anti-satellite threat. If you decide to install a tether on your satellite so you can deorbit quicker, that affects no one (indeed, there have already been several tether missions). No one is seriously proposing going up to defunct satellites to attach these things after the fact, so if that's your point, it's moot.

It really sucks that we don't seem to have any recycling capability for satellites. We spend millions to get these things in the sky, and every pound counts. You'd think a permanently spaceborne shuttle that goes around retooling and re-orbiting the damn things would be cost effective by now... Then again, given how much we like to ignore the space programs as time goes on...

At the rate AI is improving it should be possible to build what amounts to AI driven trash collectors that collect the orbiting trash. Maybe even take the stuff to the moon to be used as raw materials. Some of the pics of the trash floating around up there are amazing.

The main problem with the argument is that any solution to remove defunct satelites could be used as an anti-satellite weapon.

And since almost every nation on the planet agreed to not weaponize satellites, I don't see how any solution could pass international support.

How would tethers be used as an anti-satellite weapon? Drag-increasing airbags?

If you deorbit enemy satellites, you've stripped them of essential wartime information. You could then proceed to make a blitzkrieg, and they would have no way of knowing what is coming for them... it's an act of aggression.

I understand why anti-satellite weapons are bad.

My question was how those solutions pose an anti-satellite threat. If you decide to install a tether on your satellite so you can deorbit quicker, that affects no one (indeed, there have already been several tether missions). No one is seriously proposing going up to defunct satellites to attach these things after the fact, so if that's your point, it's moot.

issue is getting satellites that are already up, down. not outfitting new ones to self de-orbit.

The main problem with the argument is that any solution to remove defunct satelites could be used as an anti-satellite weapon.

And since almost every nation on the planet agreed to not weaponize satellites, I don't see how any solution could pass international support.

How would tethers be used as an anti-satellite weapon? Drag-increasing airbags?

If you deorbit enemy satellites, you've stripped them of essential wartime information. You could then proceed to make a blitzkrieg, and they would have no way of knowing what is coming for them... it's an act of aggression.

I understand why anti-satellite weapons are bad.

My question was how those solutions pose an anti-satellite threat. If you decide to install a tether on your satellite so you can deorbit quicker, that affects no one (indeed, there have already been several tether missions). No one is seriously proposing going up to defunct satellites to attach these things after the fact, so if that's your point, it's moot.

Having satellites in orbit that can expand their size (inflate) or extend tethers to radically adjust their course suddenly could easily be used as weapons against other satellites by ramming or impeding transmission signals. If either use radiation drag, even more so since it would offer more mobility and reflection of signals.

A satellite with neither that is setup to simply degrade it's orbit with time on a set schedule is no harm to anyone and is a known constant.

I would think any solution mounted on the satellite is going to be a flawed and limited solution. Often we want to get rid of satellites after they have stopped working. Are the retro boosters, tethers, balloons, etc going to be possible to deploy after the other functions of the satellite have failed?

Using a drag device will de-orbit a satellite but does not remove the issue of where it is going to fall. Also if you have the foresight to install a balloon you can just as easily make sure you have a de-orbit rocket on the craft. De-orbit rockets are not super precise but you can have the sat hit the pacific versus hit no particular place. If the satellite just breaks you will not be able to trigger the balloon anyway.